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Message-ID: <5e23ce30-494b-43a5-9514-7701e799e49b@arm.com>
Date: Fri, 1 Nov 2024 16:35:00 +0000
From: Steven Price <steven.price@....com>
To: Suzuki K Poulose <suzuki.poulose@....com>, kvm@...r.kernel.org,
kvmarm@...ts.linux.dev
Cc: Catalin Marinas <catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>,
Will Deacon <will@...nel.org>, James Morse <james.morse@....com>,
Oliver Upton <oliver.upton@...ux.dev>, Zenghui Yu <yuzenghui@...wei.com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Joey Gouly <joey.gouly@....com>, Alexandru Elisei
<alexandru.elisei@....com>, Christoffer Dall <christoffer.dall@....com>,
Fuad Tabba <tabba@...gle.com>, linux-coco@...ts.linux.dev,
Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
Gavin Shan <gshan@...hat.com>, Shanker Donthineni <sdonthineni@...dia.com>,
Alper Gun <alpergun@...gle.com>, "Aneesh Kumar K . V"
<aneesh.kumar@...nel.org>
Subject: Re: [PATCH v5 13/43] arm64: RME: RTT tear down
On 15/10/2024 12:25, Suzuki K Poulose wrote:
> Hi Steven
>
> On 04/10/2024 16:27, Steven Price wrote:
>> The RMM owns the stage 2 page tables for a realm, and KVM must request
>> that the RMM creates/destroys entries as necessary. The physical pages
>> to store the page tables are delegated to the realm as required, and can
>> be undelegated when no longer used.
>>
>> Creating new RTTs is the easy part, tearing down is a little more
>> tricky. The result of realm_rtt_destroy() can be used to effectively
>> walk the tree and destroy the entries (undelegating pages that were
>> given to the realm).
>>
>> Signed-off-by: Steven Price <steven.price@....com>
>> ---
>> Changes since v2:
>> * Moved {alloc,free}_delegated_page() and ensure_spare_page() to a
>> later patch when they are actually used.
>> * Some simplifications now rmi_xxx() functions allow NULL as an output
>> parameter.
>> * Improved comments and code layout.
>> ---
>> arch/arm64/include/asm/kvm_rme.h | 19 ++++++
>> arch/arm64/kvm/mmu.c | 6 +-
>> arch/arm64/kvm/rme.c | 113 +++++++++++++++++++++++++++++++
>> 3 files changed, 135 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/kvm_rme.h
>> b/arch/arm64/include/asm/kvm_rme.h
>> index bd306bd7b64b..e5704859a6e5 100644
>> --- a/arch/arm64/include/asm/kvm_rme.h
>> +++ b/arch/arm64/include/asm/kvm_rme.h
>> @@ -76,5 +76,24 @@ u32 kvm_realm_ipa_limit(void);
>> int kvm_realm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap);
>> int kvm_init_realm_vm(struct kvm *kvm);
>> void kvm_destroy_realm(struct kvm *kvm);
>> +void kvm_realm_destroy_rtts(struct kvm *kvm, u32 ia_bits);
>> +
>> +#define RME_RTT_BLOCK_LEVEL 2
>> +#define RME_RTT_MAX_LEVEL 3
>> +
>> +#define RME_PAGE_SHIFT 12
>> +#define RME_PAGE_SIZE BIT(RME_PAGE_SHIFT)
>> +/* See ARM64_HW_PGTABLE_LEVEL_SHIFT() */
>> +#define RME_RTT_LEVEL_SHIFT(l) \
>> + ((RME_PAGE_SHIFT - 3) * (4 - (l)) + 3)
>> +#define RME_L2_BLOCK_SIZE BIT(RME_RTT_LEVEL_SHIFT(2))
>> +
>> +static inline unsigned long rme_rtt_level_mapsize(int level)
>> +{
>> + if (WARN_ON(level > RME_RTT_MAX_LEVEL))
>> + return RME_PAGE_SIZE;
>> +
>> + return (1UL << RME_RTT_LEVEL_SHIFT(level));
>> +}
>> #endif
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index d4ef6dcf8eb7..a26cdac59eb3 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -1054,17 +1054,17 @@ void stage2_unmap_vm(struct kvm *kvm)
>> void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu)
>> {
>> struct kvm *kvm = kvm_s2_mmu_to_kvm(mmu);
>> - struct kvm_pgtable *pgt = NULL;
>> + struct kvm_pgtable *pgt;
>> write_lock(&kvm->mmu_lock);
>> + pgt = mmu->pgt;
>> if (kvm_is_realm(kvm) &&
>> (kvm_realm_state(kvm) != REALM_STATE_DEAD &&
>> kvm_realm_state(kvm) != REALM_STATE_NONE)) {
>> - /* Tearing down RTTs will be added in a later patch */
>> write_unlock(&kvm->mmu_lock);
>> + kvm_realm_destroy_rtts(kvm, pgt->ia_bits);
>> return;
>> }
>> - pgt = mmu->pgt;
>> if (pgt) {
>> mmu->pgd_phys = 0;
>> mmu->pgt = NULL;
>> diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
>> index f6430d460519..7db405d2b2b2 100644
>> --- a/arch/arm64/kvm/rme.c
>> +++ b/arch/arm64/kvm/rme.c
>> @@ -125,6 +125,119 @@ static int realm_create_rd(struct kvm *kvm)
>> return r;
>> }
>> +static int realm_rtt_destroy(struct realm *realm, unsigned long addr,
>> + int level, phys_addr_t *rtt_granule,
>> + unsigned long *next_addr)
>> +{
>> + unsigned long out_rtt;
>
> minor nit: You could drop the local variable out_rtt.
I could, but I was trying to avoid assuming that phys_addr_t was
compatible with unsigned long - i.e. I don't want to do the type-punning
to pass rtt_granule straight into rmi_rtt_destroy(). I would expect the
compiler will inline this function and get rid of the temporary.
>> + int ret;
>> +
>> + ret = rmi_rtt_destroy(virt_to_phys(realm->rd), addr, level,
>> + &out_rtt, next_addr);
>> +
>> + *rtt_granule = out_rtt;
>> +
>> + return ret;
>> +}
>> +
>> +static int realm_tear_down_rtt_level(struct realm *realm, int level,
>> + unsigned long start, unsigned long end)
>> +{
>> + ssize_t map_size;
>> + unsigned long addr, next_addr;
>> +
>> + if (WARN_ON(level > RME_RTT_MAX_LEVEL))
>> + return -EINVAL;
>> +
>> + map_size = rme_rtt_level_mapsize(level - 1);
>> +
>> + for (addr = start; addr < end; addr = next_addr) {
>> + phys_addr_t rtt_granule;
>> + int ret;
>> + unsigned long align_addr = ALIGN(addr, map_size);
>> +
>> + next_addr = ALIGN(addr + 1, map_size);
>> +
>> + if (next_addr > end || align_addr != addr) {
>> + /*
>> + * The target range is smaller than what this level
>> + * covers, recurse deeper.
>> + */
>> + ret = realm_tear_down_rtt_level(realm,
>> + level + 1,
>> + addr,
>> + min(next_addr, end));
>> + if (ret)
>> + return ret;
>> + continue;
>> + }
>> +
>> + ret = realm_rtt_destroy(realm, addr, level,
>> + &rtt_granule, &next_addr);
>> +
>> + switch (RMI_RETURN_STATUS(ret)) {
>> + case RMI_SUCCESS:
>> + if (!WARN_ON(rmi_granule_undelegate(rtt_granule)))
>> + free_page((unsigned long)phys_to_virt(rtt_granule));
>> + break;
>> + case RMI_ERROR_RTT:
>> + if (next_addr > addr) {
>> + /* Missing RTT, skip */
>> + break;
>> + }
>> + if (WARN_ON(RMI_RETURN_INDEX(ret) != level))
>> + return -EBUSY;
>> + /*
>> + * We tear down the RTT range for the full IPA
>> + * space, after everything is unmapped. Also we
>> + * descend down only if we cannot tear down a
>> + * top level RTT. Thus RMM must be able to walk
>> + * to the requested level. e.g., a block mapping
>> + * exists at L1 or L2.
>> + */
>
> This comment really applies to the if (RMI_RETURN_INDEX(ret) != level)
> check above. Please move it up.
Good spot.
> With that :
>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
>
Thanks,
Steve
>
>
>
>> + if (WARN_ON(level == RME_RTT_MAX_LEVEL))
>> + return -EBUSY; > +
>> + /*
>> + * The table has active entries in it, recurse deeper
>> + * and tear down the RTTs.
>> + */
>> + next_addr = ALIGN(addr + 1, map_size);
>> + ret = realm_tear_down_rtt_level(realm,
>> + level + 1,
>> + addr,
>> + next_addr);
>> + if (ret)
>> + return ret;
>> + /*
>> + * Now that the child RTTs are destroyed,
>> + * retry at this level.
>> + */
>> + next_addr = addr;
>> + break;
>> + default:
>> + WARN_ON(1);
>> + return -ENXIO;
>> + }
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int realm_tear_down_rtt_range(struct realm *realm,
>> + unsigned long start, unsigned long end)
>> +{
>> + return realm_tear_down_rtt_level(realm, get_start_level(realm) + 1,
>> + start, end);
>> +}
>> +
>> +void kvm_realm_destroy_rtts(struct kvm *kvm, u32 ia_bits)
>> +{
>> + struct realm *realm = &kvm->arch.realm;
>> +
>> + WARN_ON(realm_tear_down_rtt_range(realm, 0, (1UL << ia_bits)));
>> +}
>> +
>> /* Protects access to rme_vmid_bitmap */
>> static DEFINE_SPINLOCK(rme_vmid_lock);
>> static unsigned long *rme_vmid_bitmap;
>
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